1. Field of the Invention
The present invention relates to a method of driving a flat discharge panel capable of displaying information in the form of numerals, letters and images utilizing D.C. gas discharging and, more particularly, to a method which enables the flat discharge panel to perform a memory function.
2. Description of the Prior Arts
Conventionally, there have been opposed a variety of flat discharge panels capable of performing a memory function; some of these are typically, as follows:
(1) A.C. plasma panel (H. J. Hohen and R. A. Martel, IEEE Trans. Electron Devices, vol. ED-18, No. 9, p659, 1971); (2) D.C. memory panel with resistors (J. Smith, IEEE Trans. Electron Devices, vol. ED-20, No. 11, p1103, 1973); (3) Abnormal-glow D.C. memory panel (J. Smith and K. E. Johnson, 1974 Conf. Display Devices and systems, P110, 1974);
(4) Pulsed gas-discharged panel with memory (G. E. Holz, Symp. Soc. Information Display, Digest Papers, P36, 1972), (C.D. Lusting, et al, Symp. Soc. Information Display, Digest Papers, P128, 1974);
(5) Electron-acceleration type discharge panel
These conventional methods have, however, suffered from the following disadvantages, respectively.
The method which employs the discharge panel of the above referenced item (1) utilizes the polarity of the wall charge for performing the memory function and is capable of providing a color display only with difficulty. In addition, an unacceptably large power loss is caused by capacitive current in this device.
In the method provided by the above-referenced item (2), ballast resistors are connected in series to respective discharge display elements so that the memory function is performed by the differential between the break down voltage and the extinction voltage of the gas discharge. The memory margin is inevitably small due to the fluctuation in the ballast resistor, and the switching speed is low. In addition, the use of a negative glow lowers the luminous efficiency. Difference in luminous efficiency between the halfselect discharge cell and the non-selective discharge cell deteriorates the display performance.
The method of the above-referenced item (3) also depends on the difference between the break down voltage and the extinction voltage of the gas discharge in obtaining the memory characteristics, but maintains a high level of discharge voltage by selecting and adjusting the cathode material and the charging gas. The high discharge voltage results in a reduced efficiency. At the same time, it is pointed out that the discharge voltage and current fluctuate largely, and the switching speed is unacceptably low. The difference in the luminance between the half-select and non-select discharge cells is also evidenced in this method.
In the method of above-referenced item (4), the memory characteristics depend on a phenomenon in which the break down voltage of a pulse varies in accordance with the presence of a space charge generated by a preceding pulse. The use of pulse discharge inevitably lowers the efficiency and the range of operational margin in made narrower. In addition, A more complicated structure is required for performing the pulse discharge.
The method of the above-referenced item (5) owes its memory characteristics to a control of the space charge which is effected by optionally changing the phase-differential between main and auxiliary power pulses. In this method, a large power loss is incurred by the use of the auxiliary discharge power and the efficiency is lowered accordingly. A complicated structure is required and the power source is impractically restricted. Summary of the Invention
It is therefore an object of the invention to overcome the above described shortcomings of the prior art by providing a method of driving a flat discharge panel in which the discharge takes place only at either one of a main or an auxiliary discharging space to realize the memory function or characteristics.
According to the invention, there is provided a method in which a matrix panel having a discharge cell consisting of an X-axis anode, a Y-axis auxiliary anode and respectively cathodes which are connected in series by respective resistors is operated in such a manner that the voltages applied between the anode and the associated cathode and between the auxiliary anode and its cathode are reversed.
Other objects and advantageous features of the invention will become clear from the following description taken in conjunction with the attached drawings.